Honestly, I would avoid the K8. It’s just not a great yoyo. I have 2 Silencers and at first I thought they were slow and heavy, but after playing with them for a few months they really started to grow on me. Now I really like the Silencer and it’s one of my 3 daily throws that’s always in my backpack (along with a YYF Shutter and a YYF Replay). I haven’t thrown an N6 or April so I can’t advise you there.
If you got an N12 Shark and a Silencer as a pair I think you’d be very happy.